عنوان مقاله [English]
Biological processes are known as temperature-sensitive in wastewater treatment. Nitrification and, especially, partial nitrification (first step of nitrification) are the most temperature-sensitive among biological processes.
Factors such as dissolved oxygen, ammonia concentration, MLVSS, and etc, may influence two steps of the nitrification and organism growth rate, so nitrification should be done by controlling some of these factors.
In this study, biomass acclimation in a side stream partial nitrification sequencing batch reactor (SBR) under optimum conditions for biological nitrogen removal (BNR) has been examined. In order to show the
superiority of ammonia oxidizing biomass (AOB) over nitrite oxidizing biomass (NOB), excess sludge for solid retention time (SRT) regulation was added to another batch reactor, which had been performed under different conditions for specific ammonium oxidation rate (sAOR) evaluation and cold shock effect consideration.
Results of the side stream, partial nitrification, sequencing batch reactor showed that the specific ammonium oxidation rate at the end of any cycle and after steady state conditions was about 16.4 mgr VSS / hr.
Primary results of main stream batch tests after analysis by the Taguchi method displayed that the percent influence of consideration factors includes temperature, initial ammonium, MLVSS and time, whose specific ammonium oxidation rates were about 98.5, 0.09, 0.06 and 1.3%, respectively. So, temperature is an important factor that affects the specific ammonium oxidation rate.
More analysis on the results has shown that the effects of other factors, except the considered factor (e.g. temperature), on specific ammonium oxidation rate can be eliminated using the Taguchi method. Based on this method, it was demonstrated that abrupt cold shock caused a significant reduction in the process rate; up to 25, 55 and 78% for temperature reduction, from 30 to 25, 20 and 15$^o$C, respectively. Therefore, the temperature correction factor was calculated about 1.0965 by elimination of other factors except temperature. The temperature correction factor was also estimated to be about 1.106 using direct comparison.